Automatic-control device



Jan. 21, 1930.

F. w. HlLD 1,744,223

AUTOMATIC CONTROL DEVICE Filed Jan. 25, 1923 2 Sheets-Sheet l %S/n/7ronou-s 1 g' Asynchronous Speed Speed.

I00 I25 50 I 5 200.

200 I75 I50 I25 I00 75 50 25 0 25 50 75 I00 FU/l Load Fm Load. Load Genera fed,

WITNESSES: INVENT 4 Freder/Z W H.

/ ATTORNEY Jan. 21, 1930. 'F. w. HlLD 1,744,223

AUTOMAT IC CONTROL DEVI CE Filed Jan. 25, 1923 2 Sheets-Sheet 2 Fig. 4.

44 INVENTOR WITNESSFS: FrmW/c 14/17/74,

BY 5 ATTORNEY "Patented Jan. 21, 1930 ammo w; m, or LOS enema s, camroanm au'romrrc-oomxor. DEVICE Application aiea January 25, 1928. Serial No. 814.94g.

l My invention relates" to an automatic con- -.trol device involving a pair of alternatin f current motors with ntermediate ditierenti gearing' for controllingthe feeding movement of-a machine in accordance with' the encountered by the cutter.

Other objects oi my invention will become j evident from the following -'detailed description taken in con unction with the accompanying certain characteristicsof electric motors atare employed an connection with my invention; i

Fig. 3 is a semi-diagrammatic view of an employ my'improved method of" automatic control;

Fig. 4 is a semi-diagrammatic view of a modified form of apparatus for utilizing the principles of my invention; and

Fig. 5 is a similar view of a. further type-of apparatus utilizing the principles of my invention for another pur ose.

My invention is (particularly adapted to oil-well drilling'an the like, whereby the complicated cycle of hand-controlled operation during the rotary drilling of a well is accomplishedautomatically and at a maximum speed consistent withsafety of operation. In such. drilling operations the work ofthe driller includes several different cycles, one of which begins when the rotating bit just touches the bottom oflthe' hole and ends with the swivel that supports the drill being located close to the rotary table. That is to say, such a cycle corresponds to the completion-of'20 to 40 feet of well.

Dependin upon the'earth formations encountered tis cyclem'ay last some hours, unless interrupted. by the changing of bits for any reason. The drill will encounter both soft and hard materials and the driller has been forced in the prior art toadvance the bit intermittently in accordance with his best judgment. In other words, he frees the brake -he believes that drawings, whereiniFig. '1 and Fig. 2. are curve charts illustrating creases.

apparatus that is adapted to A itself clear. The progress of the bit, meas- .ured in'either time or distance, is thus only band from the cable so that the drummay move thro h a short arc, thus lowering the drill stem aiid allowing some of its weight to beborne b the bit as the bottom of the well is touche Then the driller tightens the brake band to hold the drum stationary until the rotating bit has cut itself clear or nearly so. This cycle must be continually repeated as the depth of the well in- 7 The pressure on the bit is a maximum at the instant of checking the drum movement, that is when the material is first encountered, but diminishes to zero when the drill cuts no one half of what it would be if-the ressure were maintained at a maximum sa e value, throughout. 'In other words, automatic feed at such constantly regulated pressure will advance the tool twice as fast as the-best hand regulation; and in actual practice this difference will probably be still greater.

I The drill pipe may Weigh as'much as 50,000 pounds, although not more thana small frac- '70 tion of this weight, for example,4,000 pounds. should actually be carried by the bit itself, the remaining weight being supp: :ted by the suspending hook. If-this ressureis exceeded, the cutting edge of'theiait will be quicklv dulled or chipped and, in many cases, still -more serious'efiects have occurred, such as bending of the drill pipe, breaking of the bit or pipe, and overstressing the drilling plant.

However, by the use of the method herein set "forth, all such troubles'are prevented. since the drilling pressure is uu muitically regulated in accordance with th=- material poses to be set forth. The drum de ice 2 is provided with the usual handbrake apparatus 6.

The drill 1 is provided with the usual square or fluted shank 7 for engaging a rotary table or bevel gear 8 and is suspended from a crown block pulley 9 by means of a..

rope or cable 10 that is wound upon the main drum portion 11 offthe draw works drum device 2. i

The two electric motors 3 and 4, the first of which is primarily adapted to effect rotary movement of the drill 1 and the other of wh ch is adapted to efiect a re ulating or controlling action, are adapted to be driven in opposite directions, as indicated by the arrows, by means ofsuitable electrical connections to a generator G or other source of energy. In-' asmuch as the particular electrical connections employed are not pertinent to my present invention, no further illustration or'descri tion thereof is considered necessary. .1 pre erably employ three-phase induct on motors,'although myinvention 15 not so limited in its application. f

The operating shaft of the driving motor 3 is shown asdirectlyconnected to a bevel gear-wheel 13 constituting one outer part of the difi'erentialmovement 5.- The operating shaft of the regulating motor 4 is ikewise shown as directly connected to a second bevel gear-wheel 15; constituting the other outer portion of the difi'erential d evice. The two gear-wheels 13 and 15 are adapted tor oint ly meshing with an intermediate or d fferential member or ear-wheel device- 19, which is mounted wit in and secured to the drum 11. It will be understood that my invention is not in any way restricted or limited'to the use of the differential movement herein shown, but

that any other device for accomplishing the 7 same results may beutilized. One other form of differential movement will be, later describedin connection with Figure 4.

For a more detailed description of the pre- -ferred form of differential movement, reference may be 'had'to my coending applica tion, Serial No. 454,451, fi ed March 22nd, 1921, for a power transmission system.

The directions of rotation of the two mo- -tors 3 and 4 are opposite, as previously mentioned and never reverse, motor 3bein ada ted to drive the gear-wheel 13 in the irection' corresponding to. lowering the load on the draw works drum 2, whereas the other motor 4 drives the gear-wheel 15 in the direction corresponding to the raising of the load upon the drum. Consequently, when the two motors 3 and 4 both run at substantially synchrowords, in the nous speed, the speed of the intermediate member, such as gear-wheel device 19 is sub stantially zero and, therefore, drum portion 11 is stationary. This corresponds to the no load condition of the drillin equipment.

When the heavy drill stem 18 hung over the suspending hook, torque is, of course, produced upon the drum member 11 and, as soon as the brake'apparatus 6 is released by the driller, the drill 1 be ins to move downwardly. The weight of t e drill during such descent will cause the drum member 11 to drive the intermediate .member 19 of the differential movement 5, which will, therefore, exert torque through the gearing upon the two electric motors 3 and 4. Consequently motor 3,

which is rotating in a direction corresponding to the descent of the drill, will be driven above synchronous s eed and will act as a generator. On the other and, motor 4, by reason of rotating in the opposite direction, will o pose the action ofthe differential device 5a n will actasamotor. g i

It will be understood that the speeds of the motors 3 and 4 will depend upon their special characteristics and also upon the gear reduc-= tion that is embodied in the differential movement 5. For the sake of simplicity, it may be considered that the motors 3 and 4 are equal in size and alike in s eed'characteristics, and handling only the'i ustrated load produced by the draw works drum 2 and the drill 1.-

Neglecting the frictio'n of the apparatus, the. speed of the motor 3 will be exactl as much above synchronism as the speed 0 the motor '4 is belowsynchronism. As is well known, the speed of the intermediate gear wheel device 19 of the differential device will at all times be equal to one half of the difference in the speeds of the gear-wheels 13 and 15 and will be in the same direction as the faster moving outer gear-wheel. In other resent case the intermediate gear-wheel device 19 will rotatein a direction corresponding to the lowering direction of the drum member 11.

For exam 1e, if the slip of the regulatin motor 4 un er the load conditions assume is 2%, its speed will thus be 98%of the synchronous speed, whilethat of the motor 3 will be.102% of synchronous speed, as indicated by the curve charts-Fig. 1 and Fig. 2- showing the relations between percentage of synchronous speed and percentage. of full load of the motors 4 and 3, respectively, undervarious operating conditions. The difierence of motor speeds, divided by two, and taking into account the gear reductions, will give the speed of o ration of the intermediate gear- The regulating motor 4 thus absorbs energy from the supply circuit under the assumed condition, whereas the other motor 3 returns energy to the supply circuit by reason of being driven as a generator above synchronous speed. Apart from the relatively small losses, the two motors substantially balance each other, and the kinetic energy of the moving load with respect to the drum member 11 is alone utilized in lowering-itself. Whenever the motor 3 is doing other work as a motor, such as driving the rotary table 8, the power produced by draw works drum 2 will thus assist the motor 3 in doing that work.

- The work of regulating motor 4 is always that of raising or tending to'raise the drill out of the well. This statement holds true at all times, including periods when the drill is actually descending. The load on the motor 4 is equal to the torque produced by the drum member 11 multi lied by that speed at which the motor may e operating in accordance with its speed curve. Since the torque upon the drum member 11 is produced by the suspended weight of the drill 1, it follows that the load of motor 4 is at all times the exact measure of that wei ht. For a further discussion of this particular feature, reference may be had to my co ending application, Serial No. 614,939 file Jan. 25, 1923, Systems of control.

The motive element perhaps best adapted for employment in my method of control is the familiar induction motor, since even relatively slight changes of torque thereof, are almost instantaneously reflected in s eed changes, whereby movement of the drill 1 may be readily and instantaneously con trolled.

A drilling cycle corresponding to the length of the drill stem will now be described.

l-Yhen the drill is descending and the bit is not yet in contact with the bottom of the hole, the weight on the hook is maximum, and the load on motor 4 is maximum for that cycle, Therefore, the speed of motor 4 is then the lowest for that cycle.

Motor 3, as previously shown, is driven above synchronous speed because of the descending drill stem. But it is also now drivin g the rotary table; this demands power even though the bit he not yet cutting, so that the actual load on motor 3 is always the resultant of the negative load produced by drum member 11 and the positive load produced by the rotary table 8. This resultant load is the leastwhen the rotating drill is descending and has not yet started to out. Therefore the speed of motor 3 is then the fastest for the cycle.

The slower the speed of motor 4, the faster that of intermediate ear-wheel device 19, and the faster the spec of motor 3, the faster that of gear-wheel device 19. So that when.

the drill is descending and not cutting we have the condition of greatest difference in the speeds of motors 4 and 3, that is, the maximum rate of movement of drum member 11 and drill 1. Thus for a given weight of drill pipe and given motor characteristics, this rate of free movement will not be exceeded under drilling conditions and the advance for each revolution of the drilling tool may be limited as desired.

Next assume that the drill bit touches bottom. Some of the weight of the drill pipe is then carried by the bit resting upon the bottom of the hole, and the weight on the hook is diminished by exactly this amount. The load on regulating motor 4 is diminished exactly in proportion to the pressure on the drill bit. Diminishing the load diminishes the slip of the motor so that'motor 4 now. runs faster.

Vhen the drill begins cutting, the load on motor 3 is increased in proportion to the diameter of the bit and the pressure on the bit. Increasing the load increases the slip, therefore, motor 3 runs slower. As the bit cuts itself clear, the reverse process takes place; the pressure on the bit lessens, the weight on the hook increases, the load on regulating motor 4 increases, the speed of motor 4 decreases. Likewise, the lessening bit pressure diminishes the resistance to the cutting tool, the load on motor 3 lessens and its speed increases. In this case, both motors 3 and 4 functionto run differential member 19 and drum member 11 faster.

Somewhere between mixumum progress and zero progress a balance will be reached and the progress will be uniform through a given substance. The rate of progress depends upon the resistance ofiered to the tool y the material being cut, but this resistance is determined by the pressure on the bit, which in turn, is proportional to the weight on the hook, the load on motor 4 and its speed.

If the bit is lowered into drilling contact .with the hardest rock material, we have the extreme conditions of zero resistance to the drill as it approaches and maximum resistance to it on making contact. Obviously, for a given pressure the slowest progress will be through this hardest material. Progress through all other materials will be faster in inverse proportion to their resistance. In particular, the rate of longitudinal advance of the cutting tool, that is, the rate of penetration, through clay is so regulated that the cuttings are very thin shavings, which the circulating mud will readily dissolve, thus preventing balled bits. As previously shown, constant pressure on the bit will be As previously stated,

It is well known that when the two bevel gears 13 and 15 rotate in opposite directions, the intermediate member 19 rotates at onehalf of the difference in their speeds and in the direction of the greater speed.

- With reference to driving motor 3 and regulating motor 4, therefore, the speed relations may be expressed by the equation,

Z.=speed of motor 3 Z,=.speed of motor 4 a Z =speed of intermediate member 19.

If the intermediate member 19 be connected to the drum 11- by a gearing or equivalent device, Equation (I) becomes 11 2,-2. K= Z5, or (III) z..-z.,=s.

where K is one-half the gear ratio change and is constant and where S =slip of motor 4 S.=slip of motor 3. When motor 3 is above synchronous speed, its'slip is negative and Equation (IV) becomes (V) S +S =S Manifestly only upon change of torque or motor characteristic can S -c ange.

Equation (V) re resents the condition when the drill is moving down freely or only slightly cutting the sides but not resting on the bottom of the hole. The equation thus represents the maximum rate of progress of the drill.

When the bit rests on the bottom, E nation (IV) takes on changed values. Let t ese be expressed by (VI) s.,s.,.=s.,, where S =the slip of motor 4 cansedby its les.-ened torque he slip of motor 3 caused by the load of the bit while cutting.

S =S minus the slip value represented by the weight of the drill now resting on the bottom.

In Equation (V), S. is caused by torque created by the descending drill stem. Therefore, when the bit is. cutting on the bottom, it first utilizes the torque represented by S, and then utilizes'the torque represented-by S The torque on the drill pipe then is proportional'to S.,+S,

When S.,=S then from Equation (VI) S =0. That is, the torsional load caused by the cutting of the bit will be limited to a value that may be readily predetermined and controlled.

For an infinitesimal period of time only can the relation v ca aadc hold true. This result follows for the reason that since S is less than S the bit is pressing on bottom and is cutting. Therefore, a balanced or compensating relation must exist 'such that S -S a equals some positive value, however small, and the bitis moving steadil downward. That is S can never equal except only by the application of load on motor 3 other than cutting. This condition might happen in boulders and the like, but evidently only sli ht increase in the torque of motor 4 will rin S, to definite zero and even to ne ative val ue, i. e., upward movement of the drill will occur.

The operation of the drilling mechanism may also be anal zed by considering the torque conditions t at prevail while the drill is cutting. From the inherent characteristics of the differential mechanism, it is apparent that the total torque exerted by themotor 4 is transmitted by means of the ear-wheel 15 to the pinions of the intermediate device 19 and by them to the gear-wheel 13 in a reversed direction. It is also apparent that the total torque of the motor 4 is impressed upon the intermediate device 19 and the drum 11. in the direction of rotation of the motor 4, as hereinbefore explained.

Under normal drilling conditions then, the total torque of the motor 4 will tend to raise the drill 1 and-the total power developed by the motor 4 will be transmitted through the differential mechanism to the gear-wheel 13 and will be utilized to turn the drill 1 in cooperation with the motor 3.

As the work of drilling progresses, it becomes necessary to increase the length of the drill ipe and, consequently, its weight so that t e torque which the drum 11 is called upon to exert becomes correspondingly reater. To provide this additional torque, it is necessary that the torque output and,

consequently, the power output of the motor 4 be increased. Since substantially all of the power output of the motor 4 is utilized for turning the drill 1, it is further necessary to reduce the power output of the motor 3 a corresponding amount in order that the total power applied to the drill 1 will remain the same.

This readjustment of the ratio of the torque supplied by the motors 3 and 4 must be made each time the weight of the drill pipe or the number of lines in the suspending tackle is chan ed in order that the pressure on the bit and t e turnin eflort applied to-it may be kept substantiallly the same.

Thus the regulation is positive, accurate, sensitive, extremely rapid and such difficulties as twistoffs, breakage, excessive stresses, binding of drill, overloads and the like will be revented. y

1 Figure 4 a different type of drilling apparatus is illustrated, including a rotary drill 30 and a traveling screw device 31 that are controlled in accordance with the 'oint action of the main driving motor 3 an the regulating motor 4, in a manner similar to that set forth in connection with Figure 3.

The drivin motor 3 again drives the rota table 8 through a suitable bevel ear 23 an also drives a belt 36, or other mec anica-l connection that is attached to a rotary nut 34, which co-operates with a traveling screw member 33. The regulatin motor 4 is provided with an operating s aft 32 having a square shank that slidabl enga es a long1tu dinal recess in one end 0 trave mg screw 33. The 0 posite end of the travelin screw is secure to the upper end of the rill 30 by means of a suitable cable 35.

The operation of the apparatus shown in Figure 4 may be set forth as follows:

Under no load conditions, that is, with no cutting action of the tool, the drive arrange ment is such that the traveling screw 33 runs faster than the rotary nut 34 and thus the drill 30 is advanced at a definite rate, as will be understood. If the speed of the main driving motor 3 remains substantially con stant while the regulating motor 4 is provide with a variable secondary resistor,

then the advance of the drill 30 and the pressure exerted thereby will respond to the slowing down of the regulatin motor 4 as it takes a load that is determin b the hardness of the material being drille The ap aratus illustrated in Figure 4 may also be utilized for horizontal earth drilling, such as tunnel boring, by substituting a horiz'ontal drill for the swivel illustrated at the left hand end of the traveling screw 33. In this case, motor 3 will drive the rotary nut 34 only, while motor 4 will drive the traveling screw 33 as already described.

In Figure 5, I illustrate the application of fiance, for example. However, such operamy method of control to an electric planer,

or the like. In this apparatus the main motor 3 drives one outer member or gear-wheel 13 of the differential device 5, while the re ulating motor 4 drives the other outer mom or or gear-wheel 15, as described in connection with Figure 3. The intermediate or differential member 18 is provided with a shaft 40 that drives a pinion or gear wheel 42 to mesh with a rack member 43. This rack member is mounted upon the movable table or platen of a planer, or the like.- Movement of the platen is effected in either direction by reason of a predetermined difference in the o erating speeds of the two motors. The di erential member 18, which drives the laten, thus rotates in the one or the other direction to produce the cutting and the return strokes.

To provide the necessary reversal in the direction of operation of the platen, a pair of dogs or levers 44 and 45 are adapted to engage switches 46 and 47', jointly, at the ends of the cutting and return strokes. In this way the speeds of the motors 3 and 4 ma be suitably changed by the movement of t e platen itself to provide the desired slow cutting stroke and rapid return stroke, as more fully hereinafter described.

\Vhenever torque is transmitted by the intermediate member 18 through shaft 40 and pinion 42 to move the platen 41, the load will e carried by the mam driving motor 3 if regulating motor 4 and the corresponding outer gear-wheel 15 be stationary. If the motor 4 and the gear-whel 15 are running, the main driving motor 3 mustalso drive the regulating motor-4 if the speed of the differential member 18 is to be maintained at'the proper value. In this case therefore, the reguating motor 4 becomes a generator to return energy to the supply circuit.

The regenerative load on the regulating motor 4 equals the actual power required to move the platen, minus the electrical losses of the regulating motor 4 and all the mechanical losses of that motor and of the driving mechanism. The motor load on the main driving motor 3 equals the regenerative load of the rcgulatin quired to move the platen 41 together with all of the electricaLand mechanical losses of the two motors 3 and 4, and the entire driving mechanism.

When the laten 41 reaches the end of a stroke, the switches 46 and 47 are operated by the corresponding dog-44 or 45 to change the speed relations of the two motors so that regulating motor 4 will now run faster than main motor 4 plus the power reving motor 3. This action reverses the direction of rotation of the differential member 18 and, therefore, the direction of operation of the platen 41. The desired speed 7 l whenever no material is actually being cut tion is well known in the art and forms no part of my present invention. I have not deemed it necessary, therefore, to further illustrate or describe such a system. In this way the actual direction of rota tion of the two motors is never changed, but only the relative values of the speeds, in order to reverse the travel of the planer parts. A very flexible planer control employing onl two machines is thus provided, together wit a regenerative braki effect in reversing-the travel of the laten. loreover the resistance encountered by the cutting tool will determine the speed of operation of the platen, which will automatically increase in speed and will automatically slow down as soon as the material is again encountered.

It will be seen that I-have thus provided a very flexible and effective method of control that is particularl adapted to any type of earth drilling, or t e like, where cutting tools are used on or in diflerent materials. This method of control automatically varies the rate of advance of the cutting tool in accordance with the material being cut and maintains the maximum rate of progress that is consistent with safety. By employing this invention the driller will not be required through the sense of touch, sight and hearing to personally endeavor to regulate the pressure and pro of the drill bit. Instead he will mere y close'the necessary electric switches, whereupon the apparatus will function automatically throug out the full len h of the drill stem, and the driller during t at time will be free to give attention to other matters.

In other words, most of the so-called accidents and supposedly unavoidable troubles in drilling, as practiced prior to the present invention, are traceable to inherently imperfect methods ofhand regulation or the like, whereas the present invention will automatically prevent the occurrences of such accidents and troubles by regulating the drilling operation in accordance with the material being drilled.

I do not wish to be restricted to the specific structural details, circuit connections or arrangement of parts herein set forth, as various modifications thereof may be made without departing from the s irit and scope of my invention. I desire, t erefore, that only such limitations shall be imposed as are indicated in the appended claims.

ry FREDERIC W. HILD. 

